Incomplete suppression of parathyroid hormone activity in sarcoidosis presenting with hypercalcaemia

An adult patient presenting in summertime with sarcoidosis and demonstrating raised levels of serum calcium and 1,25-dihydroxycholecalciferol was observed to have a serum immuno-reactive parathyroid hormone concentration in the mid-normal range. Renal function was normal. Corticosteroid administration quickly depressed serum calcium and 1,25-dihydroxycholecalciferol into the normal range; serum parathyroid hormone also fell to low levels. It was concluded that corticosteroid suppression, when incorporating measurements of serum calcium and 1,25-dihydroxycholecalciferol concentrations, can distinguish between sarcoidosis-related hypercalcaemia and primary hyperparathyroidism. The significance of the changes in parathyroid hormone concentration is obscure.